The highest contrast ratio of the Acer 223WL is 100000000:1. That's over five times the contrast ratio of the most frequently found dynamic contrast ratio of 20000000:1.
A 100000000:1 dynamic contrast ratio is in fact the best contrast ratio amongst all PC displays of a similar age and spec to the 223WL.
The worst contrast ratio across comparable types of flatpanel monitor is Mega Contrast.
It may also be worth considering one of the alternative PC screens that have a 100000000:1 dynamic contrast ratio currently available including cheaper PC monitors such as the Acer 276HL ($147.99), or the Asus VW24.